drop vs voltage drop

drop and voltage drop both are nouns.

Word	Noun	Adjective	Verb	Adverb
drop	Yes	No	Yes	No
voltage drop	Yes	No	No	No

As nouns, voltage drop is a hyponym of drop; that is, voltage drop is a word with a more specific, narrower meaning than drop:

drop: a sudden sharp decrease in some quantity
voltage drop: a decrease in voltage along a conductor through which current is flowing

Other hyponyms of drop include correction.

drop (noun)	voltage drop (noun)
the act of dropping something	a decrease in voltage along a conductor through which current is flowing
a central depository where things can be left or picked up
a curtain that can be lowered and raised onto a stage from the flies; often used as background scenery
a sudden sharp decrease in some quantity
a free and rapid descent by the force of gravity
a predetermined hiding place for the deposit and distribution of illicit goods (such as drugs or stolen property)
a steep high face of rock
a small indefinite quantity (especially of a liquid)
a shape that is spherical and small

drop (verb)	voltage drop (verb)
give birth; used for animals
grow progressively worse
go down in value
stop pursuing or acting
change from one level to another
lower the pitch of (musical notes)
fall or sink into a state of exhaustion or death
leave undone or leave out
omit (a letter or syllable) in speaking or writing
utter with seeming casualness
lose (a game)
take (a drug, especially LSD), by mouth
remove (cargo, people, etc.) from and leave
to remove
cause to fall by or as if by delivering a blow
let or cause to fall in drops
to fall vertically
let fall to the ground
fall or descend to a lower place or level
pay out
stop associating with
terminate an association with
hang loosely